1. Field of the Invention
The present invention relates to a laser-driven particle beam irradiation technology in which a target is irradiated with pulsed laser light to extract laser-driven particle rays and to use the laser-driven particle rays as irradiation particle rays used for analysis or other purposes and, in particular, to a laser-driven particle beam irradiation apparatus and also relates to a laser-driven particle beam irradiation method that controls spatial distribution and energy distribution of laser-driven particle rays while transporting the laser-driven particle ray to an object to be irradiated.
2. Description of the Related Art
There has been proposed a particle beam irradiation technique that uses an accelerator such as a synchrotron to accelerate protons or charged particles of a substance such as carbon to produce an accelerated particle beam and brings the accelerated particle beam to rest in the body of a patient to kill cancer cells (see Patent Document 1: Japanese Patent Laid-Open Publication No. 2006-341069). Such an accelerator-driven particle beam irradiation technique requires a large accelerator facility which occupies a large installation space and involves much cost for installation or maintenance. Therefore, in recent technologies, widespread use has been prohibited and the technique has been used only in a limited number of facilities.
In light of these circumstances, a laser-driven proton beam irradiation technique has been envisioned in recent years (see Patent Documents 2 and 3: Japanese Patent Laid-Open Publications No. 2007-531556 and No. 2008-022994). The laser-driven proton beam irradiation technique irradiates a cancerous portion of a patient, for example, with a proton ray extracted by irradiating a metal or polymer thin film with high-intensity and ultrashort-pulse laser light (hereinafter referred to as laser-driven proton ray). The use of laser-driven proton rays will eliminate the need for a large accelerator facility and reduce equipment in size and cost, which can lead to wider use of proton irradiation technology such as proton radiation therapy.
Laser-driven proton rays have the property of being emitted from a target at a divergence angle and spatially spreading. Therefore, when laser-driven proton rays are used for therapy radiation, the exposed dose in normal tissue surrounding a diseased site should be reduced. That is, an operation is required for converging the laser-driven proton rays in the course of transportation of the laser-driven proton rays to the diseased site.
Since the laser-driven proton rays are emitted from the target at a diversion angle, the intensity of the rays tends to deteriorate in the course of transportation to the diseased site. The deterioration of the intensity of the laser-driven proton rays makes it impossible to use the laser-driven proton rays for therapy radiation or increases the irradiation time, which may result in the burden on the patient maintained in a fixed position and posture.